This invention relates generally to a method and apparatus for diffusing a liquid condensate return stream in an industrial steam condenser to reduce erosion and corrosion on the condenser structure. More particularly, this invention relates to the use of one or more diffuser screens located intermediate a sparger nozzle and a condenser structure to diffuse the condensate stream prior to impact on the condenser structure. Still more particularly, this invention relates to a breaker screen and a diffuser screen of the type described for reducing erosion and corrosion on a condenser structure without compromising the heat transfer characteristics for which condensate is returned to a hot well in the condenser through sparger nozzles.
Steam generation systems for use in power plants, for example, are well known and highly developed. In general, such systems use a source of steam to drive a rotating machine, such as a turbine, to generate power in the form of electricity. The use of steam energy as a motive source removes energy from the steam resulting in a change of phase and the production of large amounts of condensate which travel from the turbine to a condenser. In large shell-and-tube steam condensers, the condensate is frequently pumped or gravitationally fed from various sources within the power plant to a hot well which is integral to the condenser. The hot well in the condenser serves as a reservoir for the condensate. The solid stream or streams of condensate are returned through a distribution pipe system or header arrangement to be discharged through several sparger nozzles into the condenser. For various structural and hydraulic reasons, the liquid returning to the hot well of a condenser is discharged from the spargers through sparger nozzles onto the hot well structural or functional components in great volumes and at high velocity. As a result, unwanted erosion of the condenser components results from the impingement of the rapidly moving water on those components.
In addition, a microscopic corrosion product particulate entrained in the liquid stream serves as an aggressive abrasive agent on the condenser components. Such product accelerates the erosion effect on the condenser structure. In order to alleviate these problems, many condenser manufacturers and owners have installed rigid metal baffle plates about the sparger nozzles to prevent erosion. Unfortunately, these added baffle plates have had only varying degrees of success. In certain condenser configurations, conventional solid metal baffles prove detrimental to the intended process. Occasionally, the water is deliberately sprayed onto the condenser tubes to achieve a further cooling of the fluid; however, the use of solid baffle plates can thus prevent the streams from striking the tubes and thus the desired heat transfer between the condensate return water from the sparger nozzles and the condenser tubes is adversely affected.
Occasionally, the water is introduced into the condenser in such a manner as to create a cascading or a deaerating effect inside the hot well of the condenser. In these types of structures, solid baffle plates may adversely affect the desired degree of diffusion to effect an adequate deaeration. Thus, it has remained a continuing problem in this art either to accept the adverse effects of corrosion caused by the discharge of corrosive return condensate liquid from sparger nozzles in fluid circuit with the sparger header in the condensate system, or to use metal baffle plates of the type described with the adverse affects noted, while relieving some of the adverse affects of the corrosion. Such engineering tradeoffs have not, as can be easily understood, been satisfactory.
Examples of systems for condensing turbine exhaust in power plants are shown in the U.S. Pat. Nos. 3,731,488; 4,296,802; and 4,301,861, while a representative example of sparger nozzles is shown in U.S. Pat. No. 4,322,384.
On the other hand, screens have been used for various reasons such as have been shown in U.S. Pat. Nos. 2,887,275; 3,173,614; and 4,119,276. Yet, no system has been developed which effectively uses diffuser screens located intermediate a sparger discharge nozzle and a portion of a condenser structure.
Accordingly, it is a principal object of this invention to provide a diffuser screen located intermediate a sparger nozzle for the discharge of condensate in a steam system to diffuse the fluid discharge, thus to reduce the eroding and corroding effects of the stream on the condensate.
It is another object of this invention to provide a method for diffusing fluid exiting from a sparger nozzle in a steam condensing system to reduce adverse effects of direct impingement of the liquid on the condenser structure.
It is an additional object of this invention to provide for the use of a plurality of screens located intermediate a sparger discharge nozzle and heat exchange structure in a condenser to sequentially diffuse the velocity of fluid flow of return condensate from the nozzle.
It is still an additional object of this invention to provide at least a pair of diffuser screens, at least one of which adjacent a sparger nozzle is mechanically energy absorbing, such as by movement of the screen upon fluid impact.
These and other objects of the invention will become apparent from the detailed description of the invention which follows, taken in conjunction with the accompanying drawings.